Saturated fat helps reverse metabolic syndrome and prevents diabetes

Rather than increasing the risk of heart disease and diabetes, certain saturated fats may actually reduce the risk, according to a study conducted by the National Marine Mammal Foundation and published in the journal PLOS ONE.

The most heart-healthy saturated fat was one known as heptadecanoic acid (or C17:0), which is found in whole-fat dairy products.

The study was conducted in bottlenose dolphins, which have been shown to develop a condition known as metabolic syndrome. In humans, this condition is considered a major risk factor for diabetes and cardiovascular disease. Metabolic syndrome is also sometimes called "prediabetes."

Increased intake reverses symptoms

Metabolic syndrome is defined by the presence of three or more of five possible risk factors: abdominal obesity, high triglycerides, low levels of HDL ("good") cholesterol, high fasting blood glucose, and high blood pressure. According to the Centers for Disease Control and Prevention, about one in three U.S. adults -- more than 86 million people -- have metabolic syndrome.

For the new study, the researchers measured the levels of 55 fatty acids in the blood of 49 dolphins, and they also analyzed the fatty acids found in the fish they were eating. They found that dolphins with the highest blood levels of C17:0 had the lowest levels of triglycerides and insulin.

The researchers then fed fish high in C17:0 to six dolphins who not only had low levels of that fatty acid, but also high levels of triglycerides, glucose and insulin. After six months on the new diet, the levels of all three biological markers had normalized in all six animals. Notably, blood levels of ferritin, believed to be a cause of metabolic syndrome, also decreased.

The scientists are now hoping to study how changes in the diversity of different ocean prey species could be affecting the metabolic health of wild dolphins. They are also partnering with children's hospitals to see if children diagnosed with metabolic syndrome also have low levels of C17:0.

Conventional dietary wisdom called into question

The researchers analyzed several different fish and non-ocean foods for levels of C17:0. They found that the levels of the fatty acid varied widely in seafood. High levels were found in shrimp, and the highest levels were found in mullet. Among terrestrial foods, C17:0 was found in rye, but the highest levels by far were in whole-fat dairy products.

Unsurprisingly, nonfat dairy products contained no detectable levels of C17:0, while-low fat dairy had only minimal levels. The highest levels were found in whole fat butter, with high levels also found in whole fat milk and yogurt.

"We hypothesize that widespread movement away from whole fat dairy products in human populations may have created unanticipated heptadecanoic acid deficiencies," lead researcher Stephanie Venn-Watson said, "and, in turn, this dietary deficiency may be playing a role in the global diabetes pandemic."

Given that 65 percent of the human population is lactose intolerant, however -- including 90 percent of the population in certain regions, such as East Asia -- it seems likely that either C17:0 is also found in other foods or that other saturated fats play a similar role in the human body. Certainly, the medical consensus is slowly but surely shifting away from the view that saturated fats are harmful and is once again embracing them as essential nutrients.

The research team's findings also raise other questions about the current medical consensus about labels such as "prediabetes" and "metabolic syndrome." Their finding that dolphins regularly move in and out of diabetic and metabolic syndrome states suggests that these states might be more fluid in human beings as well, in contrast to assumptions made by the dominant medical model.

Indeed, a 2014 study in the journal BMJ concluded that the American Diabetes Association's definition of "prediabetic" had no clinical value and might actually harm patients labeled as such.

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